Electronic devices are known in the art. One type of electronic device is a display device, which may include, for example, LCD devices, LED devices, OLED devices, plasma displays, flat panel display devices, touch screen devices, and/or the like. In certain cases, electronic devices may include patterned transparent electrodes, thin-films, and/or contacts. As will be appreciated, “patterned” may mean patterned with respect to conductivity and/or resistance, in some cases. In some instances, these patterned films may be addressable (e.g., via a TFT array) and may comprise a grid and/or matrix-like pattern of conductive and resistive portions of the film. In many cases, it may be desirable to provide an electrode and/or contact comprising both conductive and resistive portions in order for display devices and/or touch screen devices to function properly, e.g., as in the case with an active matrix LCD device.
The fabrication of conventional patterned transparent contacts for electronic devices typically includes depositing a continuous transparent conductive oxide layer (TCO), followed by a multi-step photolithography process to remove portions of the TCO. For instance, indium tin oxide (ITO) often is deposited on a glass substrate as a blanket layer via sputtering. The sputtered blanket layer is oftentimes patterned using a photolithographic process that includes application of a photoresist material (typically via spin coating), soft baking, exposure, hard baking, etching, and washing.
FIG. 1 is a cross-sectional view of a conventional patterned contact. As can be appreciated from FIG. 1, a TCO (e.g., ITO or the like) is disposed as a blanket layer on a substrate 1. The TCO is patterned into plural spaced apart and patterned islands 3 via photolithography, thereby defining the transparent contact. It will be appreciated that there is a step pattern and that the contact is not continuously planar.
Although photolithography is widely used, it has its drawbacks. For instance, photolithography involves many steps and many intermediate materials, increasing the time and costs associated with the products. The process in general also may increase the probability of defects during formation of the patterned layer, e.g., as a result of misalignment of the photoresist, problems with baking, incorrect exposure and/or etching, incomplete removal of the photoresist, etc. The photolithographic process also typically leaves sharp steps or “horns” that can affect subsequently applied layers and/or materials. As an example, organic light-emitting diodes (OLEDs) may be especially susceptible to this effect. Further, because in some cases the TCO material may have a refractive index that differs from the refractive index of the substrate upon which it is deposited, when portions of the TCO are removed, the visual appearance of the substrate and/or coating will appear non-uniform because of the partial presence of the TCO coating and its refractive index differences. Indeed, a typical TCO typically has an index of refraction about 2.0, whereas the supporting glass substrate typically will have an index of about 1.5. Thus, the photolithography process may result in a non-uniform appearance of the visual appearance of the article, which is an additional disadvantage. ITO itself is a high cost, and the earth's supply of indium, itself a hazardous material, also is running low.
Thus, it will be appreciated by one skilled in the art that it would be desirable to provide improved methods for forming patterned contacts, and/or electronic device made by such methods.
One aspect of certain example embodiments relates to a naturally planar thin-film transparent conductive contact, selectively patterned by means of radiative heat or the like.
Another aspect of certain example embodiments relates to a transparent contact that may include at least two adjacent layers, wherein the first layer is highly conductive and transparent (at least in the visible spectrum) with conductivity strongly dependent on the oxidation state and wherein the second layer is a transparent layer able to exchange oxygen in form of ions or atoms with the first layer at elevated temperatures.
In certain instances, the first layer is sub-oxidized and the second layer is oxidized during the deposition; and the oxygen is transferred from the second layer to the first layer to substantially suppress the conductivity during subsequent heat, IR, UV, or other exposure. In certain instances, the first layer is oxidized and the second layer is sub-oxidized during the deposition; and the oxygen is transferred from the first layer to the second layer during subsequent heat, IR, UV, or other exposure.
In some cases, the whole area of the film stack is non-conducting as deposited and becomes conductive only in the areas exposed to heat or other energy. In some cases, the whole area of the film stack is conductive as deposited and becomes non-conductive only in the areas exposed to heat or other energy.
In certain example embodiments, the selective change in the conductivity significantly affects the optical parameters of the layers only in the NIR spectral region and not in the visible, so there is very little or no noticeable difference in the visual appearance between the conductive and non-conductive areas.
In certain example embodiments, two layers may be deposited on a substrate. In certain instances, one layer may be substantially conductive and the other may be at least partially (and possibly fully) oxided. In certain other instances, both layers may be at least partially oxided. The layers may be selectively exposed to heat, radiation, and/or energy in order to facilitate the transfer of oxygen atoms between the layers. In some instances, the oxygen atoms may flow from the layer with a higher enthalpy of formation to the layer with the lower enthalpy of formation. In certain cases, this oxygen transfer may permit the conductivity of selective portions of the film to be changed. This advantageously may result in a planar contact film that is patterned with respect to conductivity and/or resistivity.
Certain example embodiments also relate to the use of planar transparent contacts in display, flat panel, touch screen, and/or other electronic devices, e.g., as an alternative to the more ubiquitously employed non-planar contact made via photolithography processes. The planar patterned contact and methods for making planar patterned contacts as described herein are based on, in some examples, the selective change of the conductivity at certain points in planar, thin-film layers. In certain example embodiments, this may be achieved through the application of heat, radiation, and/or energy (e.g., infrared radiation) to at least two thin films and/or layers. The application of heat, radiation, and/or energy in some cases may stimulate and/or facilitate the transfer of atoms affecting conductivity (e.g., oxygen atoms) between the layers. In some cases, this may create a matrix of conductive and non-conductive regions, depending on the original composition of the layers as-deposited, and/or where heat, radiation, and/or energy has been applied.
Certain example embodiments of this invention relate to a method of making a coated article comprising a multi-layer thin-film coating supported by a substrate. A conductive layer is disposed on the substrate. A sub-oxidized buffer layer is disposed on the conductive layer. An over-oxidized layer is disposed on the sub-oxidized. Energy is selectively applied to one or more portions of the coating, with the selective application of energy causing oxygen in the over-oxidized layer to migrate downward into the conductive layer to increase the resistivity of the conductive layer at the one or more portions. After the selective application of energy, the multi-layer thin-film coating is substantially planar and patterned with respect to conductivity and/or resistivity.
Certain example embodiments of this invention relate to a method of making an electronic device. A coated article including a glass substrate supporting a multi-layer thin-film coating is provided, with the multi-layer thin-film coating comprising, in order moving away from the substrate: a seed layer comprising Zn, Sn, and/or an oxide thereof, a layer comprising Ag that is conductive as deposited, a sub-oxidized buffer layer, and an over-oxidized dielectric layer. A first set of portions in the layer comprising Ag that are to be conductive portions is defined, and a second set of portions in the layer comprising Ag that are to be non-conductive portions also is defined. The coating is exposed to energy, from an energy source, in areas over the second set of portions so as to cause migration of oxygen ions or atoms from the over-oxidized dielectric layer to the layer comprising Ag and pattern the layer comprising Ag with respect to conductivity and/or resistivity. The coated article having the patterned layer comprising Ag is built into an electronic device.
Certain example embodiments of this invention relate to a method of making a coated article comprising a multi-layer thin-film coating supported by a substrate. A first layer comprising Ag and O is disposed on the substrate, with the first layer at least initially being non-conductive. A sub-oxidized buffer layer is disposed on the first layer. Energy is selectively applied to the coating proximate to the one or more portions of the first layer so as to cause oxygen at the one more portions therein to migrate upward into the sub-oxidized buffer layer to increase conductivity of the first layer at the one or more portions. After the selective application of energy, the multi-layer thin-film coating is substantially planar and patterned with respect to conductivity and/or resistivity.
Certain example embodiments of this invention relate to a method of making an electronic device. A coated article including a glass substrate supporting a multi-layer thin-film coating is provided, with the multi-layer thin-film coating comprising, in order moving away from the substrate: a seed layer comprising Zn, Sn, and/or an oxide thereof, a layer comprising Ag and O that is non-conductive as deposited, and a sub-oxidized buffer layer. A first set of portions in the layer comprising Ag and O that are to be conductive portions is defined, and a second set of portions in the layer comprising Ag and O that are to be non-conductive portions is defined. The coating, including the layer comprising Ag and O, is exposed to energy, from an energy source, in areas over the first set of portions so as to cause migration of oxygen ions or atoms from the layer comprising Ag and O into the sub-oxidized buffer layer and pattern the layer comprising Ag and O with respect to conductivity and/or resistivity. The coated article having the patterned layer comprising Ag is built into an electronic device.
These and other embodiments, features, aspect, and advantages may be combined in any suitable combination or sub-combination to produce yet further embodiments.